tW AW 

As« 



Extracts 


From the Proceedings of the California 


Geological 


Society. 




[Published in the Alta California, 1878.] 




9 5 


ALTA PRINT 










































[Published in the Alta California September 15, 1878.] 


Extracts 

From a Paper read before the State Geological Society 

By Melville Attwood, Esq., 

*\ • 

On an Improved Form of Batea, or, Gold-washer’s 

Prospecting Bowl. 


Batea is the name given to the gold-washer’s bowl, 
or vanning dish, used in the placer and gold mines of 
Brazil; a small implement which affords the most 
simple method of separating, on a limited scale, the 
grains of gold from the dirt, sand, pyritic matter, mag¬ 
netic iron, etc. The form of the batea in common use 
in Brazil is a circular, shallow wooden dish, or bowl, 
rudely fashioned with an adze and chisel, varying con¬ 
siderably in depth and size, but, nevertheless, in 
practical hands giving remarkable results. 

In 1853 I had a few bateas made of a much better 
form, the inside being turned smooth to the centre, in 
a lathe. I introduced them at that time into the mills 
under my control at Grass Valley and Agua Fria, 
where they were used for the purpose of testing or 
making mechanical assays of the tailings, blanket-wash¬ 
ings, and as a concentration to find the percentage of 
pyritic matter in the vein-stone under treatment. 

Some years ago numerous samples of sea beach, or 
gold sands, were sent to me for examination, and as 
the batea I had then in use did not separate the gold 


particles as clean and rapidly as I wished, induced me 
to make further alterations. After many trials and 
much trouble, I succeeded in getting the form I now 
use. Those persons accustomed to use the horn spoon 
or pan, would be astonished at the ease and rapidity 
with which the eold i n the sands can be washed out 
with this improved form of batea. As a concentrator 
for small parcels, or to test the working of a larger 
one, nothing that I have yet seen in operation can 
equal it. To test the value of gold quartz, Mr. Phil¬ 
lips, in his “Metallurgy of Gold and Silver,” says: 

“The most accurate results are obtained by carefully 
washing a four -pound sample in the batea. After 
having in this way concentrated the gold in about an 
ounce of sand and pyrites, this residue may be either 
subjected to assay, or the sulphides dissolved by nitric 
acid and the gold extracted by amalgamation with a 
little mercury, which is subsequently volatilized and the 
gold weighed. In either case the calculations are made 
on the four -pound sample, and when the residue has 
been subjected to fusion, very accurate results are 
obtained.” 

It is very difficult to give written directions that can 
be followed for the use of it, but a few lessons from 
those accustomed to its use will enable any one to be¬ 
come a proficient in a very short time. I will, however, 
quote the directions given by Professor W. W. Smyth 
on the use of the old form,and that of Mr. H. G. Hanks, 
more recently, in his valuable paper on “Quicksilver,” 
published in the Alta California : 

“A quantity of the material to be operated on having 
been mingled and well stirred by hand with water in 
the bowl, it is shaken from side to side and circularly, 
with a variety of movements suited to the form and to 
the nature of the ore', only to be acquired by long 
practice. The settlement and separation of the gold is 


5 


partly assisted, also, by striking one side of the bowl 
occasionally, so as to arrest the course of the particles 
for the moment; and, finally, several different layers or 
lines of mineral matter may be distinguished from one 
another, the gold occupying the lower position, then 
the magnetic iron, then the pyrites, and, lastly, other 
wastes.” 

Mr. Hanks says: 

“The manner of using the batea may be described 
as follows : Quite a quantity of water will be required, 
d his may be contained in a tank or large tub, or may 
be a convenient place near the bank of a stream or 
lake. The pulverized ore—several pounds at a time— 
is placed in the batea, which is gradually sunk in the 
water. Several times, it is broken down with the 
fingers, while the batea fioats on the water. When the 
ore is thoroughly wet and formed into mud, the batea 
is taken by the rim with both hands and again sunk in 
the water. A circular motion is then imparted to it 
(soon learned by practice). The lighter particles will 
continuously flow over the edge and sink, while the 
heavier ones collect at the centre. 

“When only a small portion remains, the batea may 
be lifted, and the water held in the depression caused 
to sweep round the centre, while one edge is slightly 
depressed. This motion will gradually remove the 
heavier particles toward the depressed part. If there 
is any gold, platinum, galena, cinnabar, or other unusu¬ 
ally heavy substance, its gravity will resist the power of 
the water, while comparatively light particles move 
slowly forward. The form of the vessel is such that 
the heaviest matter forms a point and can be closely 
observed. If there is a particle of cinnabar present, it 
will be found at the point of the prospect, clearly 
distinct from all other substances. The value of the 
batea to the prospector cannot be too highly estimated 
and it should come into more general use.” 






6 


Mr. John Roach, the well-known optician of Mont¬ 
gomery street, has used the batea, for some time, to 
assist him in some of his metallurgical investigations 
and has generally a few of them on hand. However, 
he very kindly gave me the following directions, by 
which, he says, any good turner will be able to make 
them : 

“A disk of seventeen inches diameter being turned 
conical 12 degrees, will have a depth of i-J inches from 
centre to surface. The thickness may be five-eighths of 
an inch. The outer edge, perpendicular to axis, will 
require wood 2\ inches thick for its construction ; the 
best wood, Honduras mahogany.” 

To mill-men it is a most useful instrument enabling 
them, amongst other things, to test what quicksilver is 
being carried away in the tailings. Silver ore can easily 
be separated from its gangues. The lithologist it will 
help greatly in his examination of the basaltic and 
metamorphic rocks. 

The movements of most of the large concentrators 
can be easily copied, particularly that of the percussion 
table, but with the ditierence in favor of the batea, that 
the shock, either light or hard, can be given and varied 
as required, by striking the side of the bowl with the 
hand. 


At a special meeting, held August 1st, 1878, after 
the transaction of special business, Mr. Attwood read 
the following paper “On the Milling of Auriferous 
Vein-stones.” 

At the request of some of the members of the 
Society, I have ventured to occupy part of your time 
this afternoon with a few remarks on the milling of the 



7 


different auriferous vein-stones met with in our Cali¬ 
fornia mines. 

Telluric the Only Ore of Gold—No Such Thing as 

Rebellious Gold Ores. 

In the first place, however, I wish to call your atten¬ 
tion to the condition of gold in our lodes, it being now 
generally admitted that all the gold, except that chem¬ 
ically combined with tellurium, exists in a metallic state. 

Sulphurets. 

The Californian term sulphurets, to the best of my 
recollection, was first applied to the pyritic matter that 
is found associated with quartz in the gold bearing veins 
in this State in 1859, somewhere about the time Mr. 
Deekin introduced the chlorination process for the 
extraction of gold, at his works, near Nevada City. 

The small collection of vein-stones which I now 
present to the Society, contains, besides the quartz, 
specimens of nearly all the auriferous sulphides met 
with in our mines, and are donated to the Society for 
the purpose of enabling some of the members to better 
understand what I have to say respecting the milling 
of the different descriptions of rock. 

Number one is a specimen of vein-stone from the 
Sumner Mine, Kern River. It contains sphalerite (zinc 
blende), arsenical and iron pyrites, with some small 
specks of galena. Besides the gold with the quartz, a 
large proportion is mechanically mixed and disseminated 
throughout the associated sulphides, but in extremely 
fine condition, the grains being smaller and lighter than 
those of the alluvial gold of the sea beach, or even the 
re-wash of the old river terraces by the sea. 

I selected this specimen to show that in milling vein¬ 
stone of its character, how absolutely necessary it is, 
in order to liberate the gold, to have the rock reduced 
to a very fine powder—I mean so fine that on sifting, 
90 per cent, of it would pass through a sieve having 


8 


io,ooo holes to the square inch. Now, the stamped 
vein-stone issuing from our mills is associated with gold 
in four different states : 

First —Free gold, capable of concentration with 
water. 

Second —Laminated gold, easily carried off with 
water. 

Third —Gold mechanically mixed and enclosed in 
the coarser particles of pyrites, which require to be re¬ 
duced finer to liberate the gold. 

Fourth —Telluric gold. 

The great loss in working is in the float, or laminated 
gold ; it is difficult to determine the exact amount; but 
I think it safe to say by wet stamping, even when every 
care is taken, it will amount to fully one half the free 
gold lost. 

Of the three modes of reducing vein-stone, namely: 
crushing, stamping and grinding—the first by horizon¬ 
tal rollers and rock-breakers, the second by stamps 
and the third by edge mills, pans, arastras and mill¬ 
stones—that of stamping will be found to be the most 
rapid and economical, particularly when the vein-stone 
requires to be reduced fine, so that in those mills where 
they use pans, it is a great mistake to allow the pans 
to do the work of the stamps. 

A steel iron , vastly superior , much cheaper , and 
more suitable for the construction of our mills , might 
be made from our large deposits of rich iron ore . 

The Californian stamping mills are considered the 
best of any in the world, doing a larger amount of duty 
with less wear and tear, than those made elsewhere; 
but they are costly, all the iron used in their construc- 
* tion having to be imported—a large proportion coming 
from Great Britain and paying a heavy duty. This 
might be greatly lessened if the resources of this 
country were brought into use and the iron made here. 
In difierent parts of this State there are large deposits 
of the richest kind of iron ore (magnetite) out of which 




9 


could be manufactured, direct from the ore, by the 
Catalan process, shoes, dies, tapets, and cams, at a cost 
considerably less than what is paid for ordinary castings, 
made of imported foreign iron. The iron, or rather 
semi-steel, made from the magnetite, with charcoal, by 
the Catalan process, has been used in the Brazilian 
stamping mills from their commencement. Its cost, 
delivered at their mills, is about four and a half cents 
per pound. It has two of the best properties of iron, 
namely, hardness and toughness. The cams made from 
it could hardly be broken, and, when worn, could be 
easily refaced; the shoes and dies would last out three 
or four cast iron ones, and, as the surfaces wear more 
evenly, they would reduce the rock finer and quicker 
than those made of cast iron. 

In 1867, at my request, some fifty shoes, made of the 
best Bessemer steel, were sent to one of the large Bra¬ 
zilian mills, and after a fair trial, the Brazilian mill men, 
I was told, pronounced in favor of the native iron. 

The loss of gold on treatment of such vein-stones as 
that from the Sumner mine, by either of the milling 
modes in use in California, would, if the gold contents 
did not average more than ten dollars to the ton of 
vein-stone, be at least 25 per cent., the loss on treat¬ 
ment being always greater in proportion to the poorness 
of the rock. 

If the vein-stone was rich enough to bear the extra 
expense of dry stamping and amalgamation in wooden 
barrels (iron barrels were tried, but the results obtained 
by them were not satisfactory), the same as used at 
the San Joao del Rey Mine, Brazil, the loss on treat¬ 
ment would be less than five per cent. 

Loss in Amalgamation of the Pyritic Matter in Wooden 
Barrels, Under One per Cent 

The San Joao del Rey vein-stone, when prepared 
for stamping, contains about 45 per cent, of pyritic 
matter. It is a remarkable fact that the smallest speck 




10 




of gold is rarely seen, previous to concentration, in any 
of .the vein-stones from this mine. The loss in gold by 
amalgamation of the concentrated pyritic matter (sul- 
ohurets) in wooden barrels is less than one per cent. 

See Thirty-seventh Annual Report of the Company, 
dated June, 1867.] 

Number 2 is a specimen of vein-stone from the 
Melones Mine. It contains a large proportion of tel¬ 
luric gold, or gold in chemical combination with tel¬ 
lurium, besides gold mechanically mixed with the quartz 
and pyritic matter. By the ordinary milling process, 
only the free gold would be taken up by the mercury. 
The results by assay of some of the pulverized sample 
No. 3 from the Melones Mine were $2,100 to the ton 
for gold, but only at the rate of one hundred was ob¬ 
tained by the most careful panning. 

Fine stamping with water, when the vein-stone con¬ 
tains telluric gold, would result in a serious loss, as 
telluric gold is very friable and a large proportion of it 
would be held in suspension by the water and be carried 
away with it, and, in fact, through nearly any appliances 
that might be devised for its retention ; so that the 
treatment of this character of vein-stone is just the 
opposite of those carrying pyritic matter. 

Coarse stamping being recommended, and by either 
of the ordinary milling methods in use to save all the 
tree gold, and then, by concentration, to collect all the 
heavier bodies, for sale, or to be treated by the chlo¬ 
rination process. No doubt that many of the complaints 
about not being able to save the gold may have arisen • 
from the fact of its being chemically combined with 
tellurium. 

Numbers four and five are specimens of vein-stone 
composed mostly of talc. They contain but little pyrites, 
and the gold is in tht^plates, threads and films, like 
gold leaf spread over the surface of a piece of stone. 

The stamping of such rock requires great care, as 
too heavy a flow of water through the mortars would 
carry the thin plates of gold away. The talcose matter 


» 



11 


clogs up in the mortars, so that in stamping if any gold 
quartz can be obtained, it is better to mix them 
together. 

To illustrate what I mean, a pretty test maybe made 
to show the falling speed in water of the different 
particles of gold : Take a glass tube about two feet 
long, closed at one end, and after filling it with water, 
drop in the grains oi gold you wish to try (the thin 
plates or scales will at first float on top of the water). 
Then close the open end with a cork, and turn it upside 
down and you will see plainly how long the particles 
take to reach the bottom. 

The rounded grains will sink immediately, but the 
thin scales and plates, also the laminated gold from the 
mortars, present so much more surface in proportion to 
their weight, that they take some time before they reach 
the bottom. 

Of the two ordinary modes of milling in use in this 
State, amalgamation in the batteries, with copper plates 
and what is called the blanket system, mill-men appear 
to be divided in opinion as to their respective merits. 

The blanket system may be said to have been in¬ 
troduced into the mills at Grass Valley in 1853. The 
head blanket troughs were then made in lengths of 
about six feet, and the fall from one trough to another 
was from a height of about three inches. The inclina- 
tion was at an angle of from three to five degrees with 
the horizon, but they were moveable and so arranged 
that by pressing on a small lever, the amalgamator 
could vary the inclination to suit the flow of water 
and stamped stuff from the batteries. 

The blankets first used were the common bed blan¬ 
kets, with a long nap. They were expensive, as the 
nap came off very easily, and there was great waste in 
cutting them to fit the troughs. Soon after the estab¬ 
lishment of, I think, the North Beach woolen mills, 1 
sent to San Francisco and ordered the first sluicing 
blankets. They wove them for me in long lengths, and 
the width of the troughs ; were made of a very coarse 


12 


wool, with the nap thrown up on one side, altogether a 
much better article than is now furnished to the different 
mills. 

In comparing the reports from the different Superin¬ 
tendents of the Australian gold mines and those of this 
State, the former appear to all agree on the importance 
and value of having an assay office attached to their 
works, and in ascertaining the value of the material 
operated upon, and the loss sustained in the various 
methods of treatment. Monthly statements are fur¬ 
nished of the loss by each, mill, and the actual gold 
contents of the vein-stone treated. In all of the reports 
that I have seen by our California Superintendents, 
they only give the quantity of rock stamped, sulphurets 
saved, and the results obtained from the former by 
milling and the latter by sale. They perhaps do not 
consider it of sufficient importance to publish any other 
particulars, but if no means are taken to ascertain the 
gold contents of the rock they are milling, how can 
they possibly judge of the effect of any modification 
that may have been introduced in the method of treat¬ 
ment, or that due attention has been exercised during 
the various processes to which the vein-matter has been 
subjected ? Some general idea'of loss on working may 
be obtained by sampling the tailings at regular intervals 
during the day, by placing a bucket under the sluice- 
launder, from which they finally make their escape, and 
when the bucket is full of water and stamped stuff, to 
set it aside to settle, so that the whole of the solid 
matter held in suspension is deposited before the water 
is decanted off. The deposit accumulated at the bottom 
of the bucket should then be emptied into a tub, and, 
at stated times, the contents of the tub should be dried, 
thoroughly mixed, and then submitted for assay. 

A tolerably fair estimate may be made of the gold 
contents of the rock under treatment, from the average 
result of samples taken of everything passing direct 
from the batteries, using a bucket in the same way as 
for the tailings, but at intervals of every two hours ; to 


13 


which result must also be added the cleaning up from 
the mortars. 

We too often hear of patents being applied for, for 
some new and mysterious process for the treatment of 
rebellious gold ores, and how crowds of people flock to 
interview the supposed inventors, without even first 
taking the trouble to inquire whether there was any 
such a thing as gold ores to treat, or, in other words, 
any other form of mineralized gold except telluric gold. 
There are a great many persons credited as miners and 
millmen, who have acquired any knowledge they 
possess without much practice and in an incredibly short 
time ; it is this class of men who always recommend 
any novel and crude process for the extraction of gold 
to that in use now—the result, I may say, of our past 
experience. They do not seem to be aware of how 
much has been done, written and thought on the matter 
years ago, and that, in reality, our science may be said 
to have grown out of our practice. 

The stamping mills of the present day are, undoubt¬ 
edly much superior to the old fashioned square stamps, 
but the pan, as a grinder, will not do as much work, or 
so cheaply, as a well constructed edge-mill, and is in¬ 
finitely inferior to the barrel as an amalgamator. 

The blanket system in use now is not so good as that 
introduced in Grass Valley, in 1853. 


The regular meeting of the members of the California 
State Geological Society was held August 20th, 1878. 
Mr. Melville Attwood read the following paper : 

Mineralization of Gold. 

Since the publication of the few remarks on the 
milling of auriferous vein-stones, which I made at our 
last meeting, numerous questions have been asked me 




14 


in reference to it, many still wishing to believe that 
there are such things as rebellious gold ores, so that I 
have again taken up the subject, though it would be 
impossible to do full justice to it without occupying 
more time than I have at my disposal. 

In the first place, I would suggest to any mine ad¬ 
venturer, or superintendent, working lodes which they 
think contain rebellious gold ores or mineralized gold, 
that the best argument they can use would be facts, in 
the shape of ten or fifteen-pound samples of the vein¬ 
stone, say in pieces of one or two inches square, rep¬ 
resenting, of course, quantity. They can forward such 
samples to this society free of expense (owing to the 
liberality of Messrs. Wells, Fargo & Co.), and when 
received, I will get a committe to examine and report 
on them. 

To mill-men it is not only of the greatest importance, 
but one would think absolutely necessary for the suc¬ 
cess of their operations, to have at least some knowledge 
of the true condition of the material they are working; 
otherwise it is all speculation, and can but be compared 
to groping in the dark with a faint hope of stumbling 
uDon the right treatment. 

1 o 

In ninety-nine cases out of the hundred you will find 
when people talk of having large lodes containing re¬ 
bellious gold ores, assaying very high, but that by the 
ordinary mill process they cannot save the gold, that 
the samples selected for assays were not fairly taken, and 
the real trouble arose from the fact of there being little 
or no gold in the lode to save. 

To those who feel interested on this subject, I would 
recommend the perusal of an old work: “Baron Ingo 
Born’s New Process of Amalgamation, translated into 
English by R. E. Raspe, 1791.” I will merely quote 
one passage from it in reference to the mineralization 
of gold. He says : 

“ Bergman, whose name will be immortal in chemistry, 
and whose opinion may be taken for that of all the 
chemists together, sets forth that mineralization requires 


» 


15 


the presence of a menstruum which, dissolving the 
metals, deprives them of their form and appearance ; 
and all the other combinations of metals, as likewise 
the disguises of native metals in different sorts of stone 
and matrices, are but so many different mixtures. From 
these ideas very naturally arises that common division 
of metals into native (nativa), disguised (larvata), and 
mineralized (mineralizata).” 

In a note at the end of the same section, he says : 

“ I use here the name of gold ores without employing 
the least idea of their mineralization, or calciform state 
—which, in my opinion, never exists—I mean to express 
that gold particles, small and indivisible are disguised in 
them, and wrapt up in other minerals.” 

Richard Kirwan, in his “Elements of Mineralogy,” 
published in i 796, absolutely denies the mineralization 
of gold; and says: “gold being incapable, in low heats, 
of uniting with pure air, sulphur, arsenic, or any acid 
furnished by nature, it is plain it can never be mineral¬ 
ized, in the strict sense ol the word. 

I have quoted from these old authorities to show that 
the question of gold ores is by no means new. I trust, 
however, for the future, such terms as “rusty gold,” 
and “rebellious gold ores,”' will be found only in their 
proper place, among the list of “vulgar errors.” 

The gold on the Comstock lode is argentiferous, and 
occurs, more or less, in an .unchanged form and compo¬ 
sition throughout the whole length of the lode, and 
from the croppings to the deepest workings. Its di¬ 
minished value is caused by the silver alloy. It con¬ 
sists—53.37 per cent, gold, 42.87 silver, and 1.76 of 
substances as yet undetermined. 

I have just been handed a copy of the Forty-eighth 
Annual Report of the San Joao del Rey Company, 
Brazil, dated London, June, 1878. It appears that, 
during the year, they stamped 62,745 tons, and that the. 
mean loss on treatment was 31 percent. I he gold con¬ 
tents of the vein-stone, about $21 per ton. The aver¬ 
age width of lode, 42 feet; length of stoping ground, 




10 


600 feet; stamps, duty* with heads, 135 ; working days, 
355.44; tons stamped/62,745 ; tons per day, 176.53. 

In their report of June, 1867, they stamped 60,685 
tons, with a loss of only 14.92 per cent. No explana¬ 
tion is given for the great difference in loss, but their 
straking, or mode of concentration, must be defective. 

The company might do well to try some of our Cali¬ 
fornia Concentrators. Mr. J. Hendy’s concentrators 
have been used in this country for a great number of 
years, and appear to have made very clean work. 

In reply to the questions respecting the Catalan pro¬ 
cess, it is one of the most primitive modes of making 
iron, and the cost of the furnace, forge and trompe, 
would not be much more than that required to build 
and fit up a good blacksmith shop. 

If we made our own iron, it would give employment 
and bread to the many, instead of the enrichment of 
the few, which appears to be the result of importing it. 










